Pyroxasulfone and glutamine synthesis inhibitor compositions for weed control

ABSTRACT

The present invention is directed to compositions containing herbicidal mixtures of pyroxasulfone and glutamine synthesis inhibitors. The present invention is further directed to methods of increasing the activity of a glutamine synthesis inhibitor with the compositions of the present invention.

FIELD OF THE INVENTION

The present invention relates to agricultural compositions useful forcontrolling weeds, and methods of use thereof.

BACKGROUND OF THE INVENTION

Unwanted plants, such as weeds, reduce the amount of resources availableto crop plants and can have a negative effect on crop plant yield.Commonly unwanted plants in crop plant environments include broadleafplants and grasses.

Herbicides are used to kill unwanted plants, such as weeds, in cropplant environments. Herbicides are expensive, and their use may resultin unintentional consequences such as groundwater contamination,environmental damage, herbicide-resistant weeds, and human and mammalianhealth concerns. It is therefore desirable to minimize the amount ofherbicides applied to a crop-growing environment or any area in need ofweed control.

Unwanted plants, such as weeds, may greatly reduce yields of cropplants. For example, a Horseweed infestation reportedly was responsiblefor an 80% reduction in soybean yields. Bruce, J. A., and J. J. Kells,Horseweed (Conyza Canadensis) control in no-tillage soybeans (Glycinemax) with preplant and preemergence herbcides, Weed Technol. 4:642-647(1990). Therefore, controlling weeds, and especially grasses andHorseweed, is a major concern of crop growers.

Further, Horseweed and other grasses are becoming resistant to thewidely used herbicide glyphosate. As early as 2000, glyphosate resistantHorseweed was reported in Delaware. Glyphosate resistant Horseweed hassince been reported in numerous states. Accordingly, there is a need fornew products that can provide effective kill rates of glyphosateresistant Horseweed.

Weeds are also becoming resistant to herbicides that inhibitacetolactate synthase (ALS) and protoporphyrinogen oxidase (PPO).Horseweed has also been reported to be resistant to 2,4-D and dicamba.Accordingly, there is a need for new technology to control weeds thatare resistant to commercially available herbicides.

In most fields throughout the Midwest and Mid-South, in-crop burndownapplications are the only options for controlling Horseweed due toweather and timeliness of applications. Repeated applications of thesechemistries have contributed to expanding resistance and lack ofcontrol. Repeated applications of single effective active ingredientswill only continue to select for resistant populations of weeds, thusleaving no alternatives for weed control other than mechanical.Mechanical removal of weeds requires extensive use of resources and isnot an option for no-till or highly erodible land.

No-till farming has been increasing in popularity because it has manybenefits, including decreased labor time and decreased soil erosion.However, one of the downsides of no-till farming is that weeds areharder to control in these areas because they are not subjected totilling. Accordingly, there is an increasing need for alternative waysto handle weed infestation.

Pyroxasulfone (3-[[[5-(difluoromethoxy)-1-methyl-3(trifluoromethyl)-1H-pyrazol-4-yl]methyl]sulfonyl]-4,5-dihydro-5,5-dimethylisoxazole)is an herbicide that has residual weed control. Pyroxasulfone, however,does not have post emergence weed control. Pyroxasulfone is commerciallyavailable in a mixture with flumioxazin (Fierce®, available from ValentU.S.A. Corporation).

Glufosinate (DL-4-[hydroxy](methyl)phosphinoyl]-DL-homoalaninate) andits salts such as DL-glufosinate-ammonium are known to have herbicidalactivity and are commercially available, e.g. Basta™ and Liberty™(available from Bayer CropSciences). Glufosinate is a phosphinic acidthat inhibits the activity of glutamine synthetase which results inammonium accumulation in the plants. The ammonia destroys the cellswhich inhibits photosynthesis. Bialaphos is another glutamine synthesisinhibitor that is naturally produced by a soil microorganism.

When applied alone, glufosinate often yields unsatisfactory weedcontrol. Several applications and/or high dosage rates are required forhigh efficacy. Further, glufosinate has little effect of some broadleafspecies and rhizomatous grasses. In an effort to overcome theseshortcomings, glufosinate is frequently applied with at least oneadditional herbicide, such as 2,4-D, dicamba, triazines such as atrazineor metribuzin, chloroacetanilides such as metholachloror dimethenamid(including dimethenamid-P), linuron and/or pendimethalin. However, theeffectiveness of such combinations is often not satisfactory and highapplication rates are still required to achieve acceptable control ofgrass weeds and broadleaves. Moreover, the reliability of suchcombinations depends strongly on the weathering conditions and certaindifficult to control weed species may escape. In addition, theherbicidal activity of these compositions persists only for a shorttime, which allows effective burndown only within a small timeframeprior to planting a crop. Moreover, the persistence of the herbicidalactivity strongly depends upon the weathering conditions.

U.S. Patent Application Publication No. 2011/0065579 discloses thousandsof mixtures of herbicides, one of which is a mixture of glufosinate andpyroxasulfone in a ratio range of from 2000:1 to 1:10. However, thispublication fails to provide guidance within this broad range ofacceptable amounts of glufosinate or pyroxasulfone. Further, thispublication does not teach or suggest narrower ratios that would produceacceptable results. In addition, this publication fails to suggest thesynergy that Applicants discovered between glutamine synthesisinhibitors and pyroxasulfone.

In summary, there is a need for a composition that reduces the amount ofherbicides necessary to obtain sufficient weed control while minimizingthe harm to crop plants. As more weeds become resistant to herbicides,alternative compositions with high weed control are desired. Further, asno-till farming continues to increase in popularity, there is a greaterneed for effective herbicides. A composition with effective weed controland lower dosage rate will lead to increased crop plant yields, anddecreased environmental, human, and mammalian health concerns.

SUMMARY OF THE INVENTION

In one aspect, the present invention is directed to agriculturalcompositions comprising pyroxasulfone and a glutamine synthesisinhibitor, or an agriculturally acceptable salt thereof, in a ratio offrom about 1:0.5 to about 1:20.

In another aspect, the present invention is directed to methods forincreasing the activity of a glutamine synthesis inhibitor comprisingapplying the agricultural compositions of the present invention to anarea in need of weed control.

DETAILED DESCRIPTION OF THE INVENTION

It was surprisingly discovered that pyroxasulfone can significantlyincrease the burndown activity of glutamine synthesis inhibitors whenapplied to weeds by as much as 3-fold compared to a glutamine synthesisinhibitor applied alone. This finding was unexpected becausepyroxasulfone applied by itself has no post emergent control.

Compositions of the present invention containing a mixture ofpyroxasulfone and at least one glutamine synthesis inhibitor, or anagriculturally acceptable salt thereof, will provide the end user withconsistent herbicidal activity. The compositions will also provideresidual weed and grass control.

In one embodiment, the present invention is directed to agriculturalcompositions comprising pyroxasulfone and a glutamine synthesisinhibitor, or an agriculturally acceptable salt thereof, in a ratio offrom about 1:0.5 to about 1:20. In a preferred embodiment, thecompositions contain from about 1:1 to about 1:10 ofpyroxasulfone:glutamine synthesis inhibitor, or an agriculturallyacceptable salt thereof In a more preferred embodiment, the compositionscontain from about 1:3 to about 1:8 of pyroxasulfone:glutamine synthesisinhibitor, or an agriculturally acceptable salt thereof. In an even morepreferred embodiment, the compositions contain from about 1:4 to about1:7 of pyroxasulfone:glutamine synthesis inhibitor, or an agriculturallyacceptable salt thereof In a most preferred embodiment, the compositionscontain from about 1:5 to about 1:6.6 of pyroxasulfone:glutaminesynthesis inhibitor, or an agriculturally acceptable salt thereof.

The glutamine synthesis inhibitor of the present invention can beselected from any herbicide that is classified by the HerbicideResistance Action Committee (“HRAC”) as group H or the Weed ScienceSociety of America (“WSSA”) as group 14. In another embodiment, theglutamine synthesis inhibitor in compositions of the present inventionis glufosinate, an agriculturally acceptable salt thereof, or bialaphos.In a preferred embodiment, the glutamine synthesis inhibitor isglufosinate. In a more preferred embodiment, the glutamine synthesisinhibitor is the ammonium salt of glufosinate.

In yet another embodiment, the compositions of the present inventionalso contain an herbicide classified by HRAC as group E or the WWSA asgroup 14 (inhibitors of protoporphyrinogen oxidase). In a preferredembodiment, this herbicide is flumiclorac or flumiclorac-pentyl.Flumiclorac (2-[2-chloro-4-fluoro-5-(1,3,4,5,6,7-hexahydro-1,3-dioxo-2H-isoindol-2-yl)phenoxy]acetic acid) is adicarboximide herbicide that has preemergence activity.

In an embodiment, the present invention is directed to methods forincreasing the activity of a glutamine synthesis inhibitor comprisingapplying an agricultural composition comprising pyroxasulfone and aglutamine synthesis inhibitor, or an agriculturally acceptable saltthereof, in a ratio of about 0.05 to about 1:20, or from about 1:1 toabout 1:10 to an area in need of weed control. In a preferredembodiment, the compositions that are applied to the area in need ofweed control contain from about 1:3 to about 1:8 ofpyroxasulfone:glutamine synthesis inhibitor, or an agriculturallyacceptable salt thereof In a more preferred embodiment, the compositionsthat are applied to the area in need of weed control contain from about1:4 to about 1:7 of pyroxasulfone:glutamine synthesis inhibitor, or anagriculturally acceptable salt thereof. In a most preferred embodiment,the compositions that are applied to the area in need of weed controlcontain from about 1:5 to about 1:6.6 of pyroxasulfone:glutaminesynthesis inhibitor, or an agriculturally acceptable salt thereof

In an embodiment, from about 50 to about 150 grams per hectare ofpyroxasulfone is applied to the area in need of weed control. In apreferred embodiment, from about 70 to about 110 grams per hectare ofpyroxasulfone is applied to the area in need of weed control. In a morepreferred embodiment, from about 80 to about 100 grams per hectare ofpyroxasulfone is applied to the area in need of weed control. In a mostpreferred embodiment, about 90 grams per hectare of pyroxasulfone isapplied to the area in need of weed control.

In an embodiment, from about 100 to about 1,000 grams per hectare ofglutamine synthesis inhibitor is applied to the area in need of weedcontrol. In a preferred embodiment, from about 300 to about 700 gramsper hectare of glutamine synthesis inhibitor is applied to the area inneed of weed control. In a more preferred embodiment, from about 400 toabout 650 grams per hectare of glutamine synthesis inhibitor is appliedto the area in need of weed control. In a most preferred embodiment,from about 450 to about 600 grams per hectare of glutamine synthesisinhibitor is applied to the area in need of weed control.

In an embodiment, from about 100 to about 1,000 grams per hectare ofglufosinate, or an agriculturally acceptable salt thereof, is applied tothe area in need of weed control. In a preferred embodiment, from about300 to about 700 grams per hectare of glufosinate, or an agriculturallyacceptable salt thereof, is applied to the area in need of weed control.In a more preferred embodiment, from about 400 to about 650 grams perhectare of glufosinate, or an agriculturally acceptable salt thereof, isapplied to the area in need of weed control. In a most preferredembodiment, from about 450 to about 600 grams per hectare ofglufosinate, or an agriculturally acceptable salt thereof, is applied tothe area in need of weed control.

In another embodiment of the invention, flumiclorac-pentyl is alsoapplied to the area in need of weed control. In an embodiment, fromabout 14 to about 116 grams per hectare of flumiclorac-pentyl is appliedto the area in need of weed control. In a preferred embodiment, fromabout 14 to about 90 grams per hectare of flumiclorac-pentyl is appliedto the area in need of weed control. In a most preferred embodiment,from about 14.5 to about 73 grams per hectare of flumiclorac-pentyl isapplied to the area in need of weed control.

In a further embodiment, the weed controlled by the compositions of thepresent invention is at least one of Horseweed (Conyza Canadensis),Large Crabgrass (Digitaria sanguinalis), Palmer Amaranth (Amaranthuspalmen), Broadleaf Signalgrass (Brachiaria platyhylla), CommonBarnyardgrass (Echinochloa crus-galli), Yellow Nutsedge (Cyperusesculentus), Eclipta (Eclipta prostrate), Lamb's quarters (Chenopodium),Velvetleaf (Abutilon theophrasti), and Giant Foxtail (Setaria faberi).In a preferred embodiment, the weed controlled is Palmer Amaranth. Inanother preferred embodiment, the weed controlled is Horseweed.

In an embodiment of the invention, the pyroxasulfone and glutaminesynthesis inhibitor, or an agriculturally acceptable salt thereof, areapplied concurrently to the area in need of weed control. In anotherembodiment, the pyroxasulfone and glutamine synthesis inhibitor, or anagriculturally acceptable salt thereof, are applied sequentially to thearea in need of weed control.

In a preferred embodiment, the glutamine synthesis inhibitor of thepresent invention is glufosinate. In another preferred embodiment, theglutamine synthesis inhibitor of the present invention is the ammoniumsalt of glufosinate.

Applicants' mixtures can be applied by any convenient means. Thoseskilled in the art are familiar with the modes of application thatinclude foliar applications such as spraying, chemigation (a process ofapplying the mixture through the irrigation system), by granularapplication, or by impregnating the mixture on fertilizer.

Applicants' mixtures can be prepared as concentrate formulations or asready-to-use formulations. The mixtures can be tank mixed.

The herbicide mixtures of the present invention may be formulated tocontain adjuvants, such as solvents, anti-caking agents, stabilizers,defoamers, slip agents, humectants, dispersants, wetting agents,thickening agents, emulsifiers, and preservatives which increase thelong lasting activity of the actives. Other components that enhance thebiological activity of these ingredients may optionally be included.

Methylated seed oil (“MSO”) is an adjuvant that improves leaf cuticlepenetration of an agricultural active, such as a plant growth regulator,fungicide or herbicide. MSO can be used in the mixtures of the presentinvention, but is not required or responsible for the synergy of thecombination the herbicides of the present invention. Other oil basedadjuvants with similar qualities could also be used, such as crop oilconcentrates.

Mixtures of the present invention can be formulated to contain a liquidsolvent. Examples of solvents include water or oil concentrates.

Applicants' mixtures can also include one or more additional herbicides.

The mixtures of the present invention can be applied to any environmentin need of weed control. The environment in need of weed control mayinclude any area that is desired to have a reduced number of weeds or tobe free of weeds. For example, the herbicide combination can be appliedto an area used to grow crop plants, such as a field, orchard, orvineyard. For example, Applicants' compositions and methods can beapplied to areas where soybeans, corn, peanuts, and cotton are growing.In a preferred embodiment, the mixture is applied in an area where abroadleaf crop (soybean, cotton, peanut, orchard, vineyard, forages) isgrowing. The mixtures of the present invention can also be applied tonon-agricultural areas in need of weed control such as a lawns, golfcourses, or parks.

Applicants' compositions and methods can be applied successfully to cropplants and weeds that are resistant to glyphosate, glufosinate, or otherherbicides. The composition and methods can also be applied to areaswhere genetically modified crops (“GMOs”) or non-GMO crops are growing.The term “GMO crops” as used herein refers to crops that are geneticallymodified.

When used in this application, Horseweed refers to Conyza Canadensis,Large Crabgrass refers to Digitaria sanguinalis, Palmer Amaranth refersto Amaranthus palmeri, Broadleaf Signalgrass refers to Brachiariaplatyhylla, Common Barnyardgrass refers to Echinochloa crus-galli,Yellow Nutsedge refers to Cyperus esculentus, Eclipta refers to Ecliptaprostrata. Although the composition of the present invention has provensynergy when applied to Horseweed and Palmer amaranth, the synergisticcomposition could be applied to any number of other weeds or undesiredplants for effective control and is not limited to the examples. Thesecould include Giant Ragweed (Ambrosia trifida), Common Ragweed (Ambrosiaartemisiifolia), and Velvetleaf (Abutilon theophrasti).

Throughout the application, the singular forms “a,” “an,” and “the”include plural reference unless the context clearly dictates otherwise.

As used herein, all numerical values relating to amounts, weightpercentages and the like are defined as “about” or “approximately” eachparticular value, plus or minus 10%. For example, the phrase “at least5.0% by weight” is to be understood as “at least 4.5% to 5.5% byweight.” Therefore, amounts within 10% of the claimed values areencompassed by the scope of the claims.

As used herein, “post emergence” refers to an herbicide treatment thatis applied to an area after the weeds have germinated and emerged fromthe ground or growing medium.

As used herein, “burndown” refers to when an herbicide is used to reduceweed presence at the time of treatment. Burndown is often used inminimum or no-till fields because the weeds cannot be managed by tillingthe soil. The burndown application may be used post-harvest and/or priorto crop emergence. Burndown is especially useful against weeds thatemerge between growing seasons.

As used herein, synergy means that when combined, the claimedcomposition achieves a result that is greater than the expected result.

These representative embodiments are in no way limiting and aredescribed solely to illustrate some aspects of the invention.

Further, the following example is offered by way of illustration onlyand not by way of limitation.

EXAMPLE Example 1

The following field test was conducted. Roundup Ready soybeans (Glycinemax) were used in the test as the crop plant. All of the treatmentscontained MSO concentrate oil at 1% v/v.

When the test began, the test plot had weeds that were less than 24inches tall. Treatments were administered at the concentrations asfollows. Glufosinate-ammonium was administered at 593 grams/hectare.Pyroxasulfone was administered at 90 grams/hectare throughout theexperiment.

On 14 DAT, readings were taken to determine the survival of PalmerAmaranth. On 21 DAT, readings were taken to determine the residualcontrol of Palmer Amaranth and Horseweed. Survival ratings were taken bycounting the number of alive and dead plants at the time of the reading.All data was analyzed using Bartlett's test and with p value of 0.5 fordetermining significance of the results. The results of this study canbe seen below in “Table 1. The Effect of Glufosinate and Pyroxasulfoneon Weeds.”

TABLE 1 The Effect of Glufosinate and Pyroxasulfone on Weeds Rate (gramsResidual of active Palmer control of per amaranth Palmer HorseweedHerbicide hectare) (<2″ tall) amaranth (bolted) 1 glufosinate 593 90 9375 2 pyroxasulfone 90 5 99 0 3 glufosinate 593 99 99 97 pyroxasulfone 904 glufosinate 593 99 99 99 pyroxasulfone 90 flumiclorac- 73 pentyl

The results illustrate that a composition of glufosinate andpyroxasulfone is synergistic. Pyroxasulfone alone provides only 5%control of Palmer Amaranth, however, when combined with glufosinate, thecombination provided a 99% kill rate. Glufosinate alone could onlyachieve a 90% kill rate. For Horseweed, pyroxasulfone provides no (zeropercent) residual control of Horseweed. In contrast, the combination ofpyroxasulfone and glufosinate provided a 97% kill rate.

What is claimed is:
 1. An agricultural composition comprisingpyroxasulfone and a glutamine synthesis inhibitor, or an agriculturallyacceptable salts thereof, in a ratio of from about 1:0.5 to about 1:20.2. The composition of claim 1 wherein the ratio of pyroxasulfone and aglutamine synthesis inhibitor is from about 1:3 to about 1:8.
 3. Thecomposition of claim 1 wherein the ratio of pyroxasulfone and aglutamine synthesis inhibitor is from about 1:4 to about 1:7.
 4. Thecomposition of claim 1 wherein the glutamine synthesis inhibitor isselected from the group consisting of glufosinate, an agriculturallyacceptable salt thereof, and bialaphos.
 5. The composition of claim 4wherein the glutamine synthesis inhibitor is glufosinate or anagriculturally acceptable salt thereof.
 6. The composition of claim 1further comprising flumiclorac-pentyl.
 7. A method of increasing theactivity of a glutamine synthesis inhibitor comprising applying anagricultural composition comprising pyroxasulfone and a glutaminesynthesis inhibitor in a ratio of from about 1:0.5 to about 1:20 to anarea in need of weed control.
 8. The method of claim 7 wherein thepyroxasulfone is applied at a rate of from about 50 to about 150 gramsper hectare.
 9. The method of claim 7 wherein the pyroxasulfone isapplied at a rate of from about 70 to about 110 grams per hectare. 10.The method of claim 7 wherein the pyroxasulfone is applied at a rate offrom about 80 to about 100 grams per hectare.
 11. The method of claim 7wherein the glutamine synthesis inhibitor is applied at a rate of fromabout 100 to about 1000 grams per hectare.
 12. The method of claim 7wherein the glutamine synthesis inhibitor is applied at a rate of fromabout 300 to about 700 grams per hectare.
 13. The method of claim 7wherein the glutamine synthesis inhibitor is applied at a rate of fromabout 450 to about 600 grams per hectare.
 14. The method of claim 7wherein the glutamine synthesis inhibitor is glufosinate.
 15. The methodof claim 7 further comprising applying flumiclorac-pentyl to the area inneed of weed control.
 16. The method of claim 7 wherein the weedcontrolled is selected from the group consisting of Horseweed (ConyzaCanadensis), Large Crabgrass (Digitaria sanguinalis), Palmer Amaranth(Amaranthus palmen), Broadleaf Signalgrass (Brachiaria plathylla),Common Barnyardgrass (Echinochloa crus-galli), Yellow Nutsedge (Cyperusesculentus), Eclipta (Eclipta prostrate), Lamb's quarters (Chenopodium),Velvetleaf (Abutilon theophrasti), and Giant Foxtail (Setaria faberi).17. The method of claim 16 wherein the weed controlled is PalmerAmaranth.
 18. The method of claim 16 wherein the weed controlled isHorseweed.
 19. The method of claim 7 wherein the pyroxasulfone andglutamine synthesis inhibitor, or agriculturally acceptable saltthereof, are applied concurrently or sequentially to the area in need ofweed control.
 20. The method of claim 19 wherein the glutamine synthesisinhibitor is glufosinate.